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jonny [76]
2 years ago
8

Can anyone help me with this last question?

Physics
1 answer:
Digiron [165]2 years ago
6 0

Answer:

v = 39.6 m/s (first answer option)

Explanation:

Use conservation of mechanical energy.

The starting is completely potential energy and the final is all kinetic energy:

m*g*h=\frac{1}{2}*m*v^2\\g *  h=\frac{1}{2} v^2\\9.8*80=\frac{1}{2} v^2\\v^2=1568\\v\approx 39.6\,\,m/s

which agrees with the first answer shown.

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A motorist enters a freeway at 45 km/h and accelerates uniformly to 99 km/h. From the odometer in the car, the motorist knows th
Marat540 [252]

Answer:

a)  19440 km/h²

b) 10 sec

Explanation:

v₀ = initial velocity of the car = 45 km/h

v = final velocity achieved by the car = 99 km/h

d = distance traveled by the car while accelerating = 0.2 km

a = acceleration of the car

Using the kinematics equation

v² = v₀² + 2 a d

99² = 45² + 2 a (0.2)

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b)

t = time required to reach the final velocity

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t = 0.00278 h

t = 0.00278 x 3600 sec

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2 years ago
The wavelength of red helium-neon laser light in air is 632.8 nm.(a) What is its frequency? Hz(b) What is its wavelength in glas
vekshin1
<h2>Answers:</h2>

The speed of a wave is given by:

v=f.\lambda  (1)

Where f is the frequency and  \lambda the wavelength.

In the case of light, its speed is:

c=f.\lambda (2)

On the other hand, the described situation is known as Refraction,   a phenomenon in which the light changes its direction when passing through a medium with a refractive index different from the other medium.  

In this context, the Refractive index n is a number that describes how fast light propagates through a medium or material, and is defined as the relation between the speed of light in vacuum (c=3(10)^{8}m/s) and the speed of light v in the second medium:

n=\frac{c}{v} (3)

In addition, as the light changes its direction, its wavelength changes as well:

n=\frac{\lambda_{air}}{\lambda_{glass}} (4)

Knowing this, let's begin with the answers:

<h2>a) Frequency</h2>

From equation (2) we can find f:

f=\frac{c}{\lambda}  (5)

Knowing that 1nm=(10)^{-9}m:

f=\frac{3(10)^{8}m/s}{632.8(10)^{-9}m}  

f=4.74(10)^{14}Hz}     (6)   >>>Frequency of the helium-neon laser light

<h2>b) Wavelength in glass</h2>

We already know the wavelength of the light in air \lambda_{air} and the index of refraction of the glass.

So, we only have to find the wavelength in glass \lambda_{glass} from equation (4):

\lambda_{glass}=\frac{\lambda_{air}}{n}

\lambda_{glass}=\frac{632.8(10)^{-9}m}{1.48}

\lambda_{glass}=427(10)^{-9}m=427nm   (7)   >>>Wavelength of the helium-neon laser light in glass

<h2>c) Speed in glass</h2>

From equation (3) we can find the speed vof this light in glass:

v=\frac{c}{n}

v=\frac{3(10)^{8}m/s}{1.48}

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